<!DOCTYPE html>
<html>
<!-- Created by GNU Texinfo 7.1, https://www.gnu.org/software/texinfo/ -->
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<!-- This file documents the use of the GNU compilers.

Copyright © 1988-2023 Free Software Foundation, Inc.

Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.3 or
any later version published by the Free Software Foundation; with the
Invariant Sections being "Funding Free Software", the Front-Cover
Texts being (a) (see below), and with the Back-Cover Texts being (b)
(see below).  A copy of the license is included in the section entitled
"GNU Free Documentation License".

(a) The FSF's Front-Cover Text is:

A GNU Manual

(b) The FSF's Back-Cover Text is:

You have freedom to copy and modify this GNU Manual, like GNU
     software.  Copies published by the Free Software Foundation raise
     funds for GNU development. -->
<title>MIPS Paired-Single Support (Using the GNU Compiler Collection (GCC))</title>

<meta name="description" content="MIPS Paired-Single Support (Using the GNU Compiler Collection (GCC))">
<meta name="keywords" content="MIPS Paired-Single Support (Using the GNU Compiler Collection (GCC))">
<meta name="resource-type" content="document">
<meta name="distribution" content="global">
<meta name="Generator" content="makeinfo">
<meta name="viewport" content="width=device-width,initial-scale=1">

<link href="index.html" rel="start" title="Top">
<link href="Indices.html" rel="index" title="Indices">
<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
<link href="Target-Builtins.html" rel="up" title="Target Builtins">
<link href="MIPS-Loongson-Built_002din-Functions.html" rel="next" title="MIPS Loongson Built-in Functions">
<link href="MIPS-DSP-Built_002din-Functions.html" rel="prev" title="MIPS DSP Built-in Functions">
<style type="text/css">
<!--
a.copiable-link {visibility: hidden; text-decoration: none; line-height: 0em}
div.example {margin-left: 3.2em}
kbd.key {font-style: normal}
span:hover a.copiable-link {visibility: visible}
-->
</style>


</head>

<body lang="en_US">
<div class="subsection-level-extent" id="MIPS-Paired_002dSingle-Support">
<div class="nav-panel">
<p>
Next: <a href="MIPS-Loongson-Built_002din-Functions.html" accesskey="n" rel="next">MIPS Loongson Built-in Functions</a>, Previous: <a href="MIPS-DSP-Built_002din-Functions.html" accesskey="p" rel="prev">MIPS DSP Built-in Functions</a>, Up: <a href="Target-Builtins.html" accesskey="u" rel="up">Built-in Functions Specific to Particular Target Machines</a> &nbsp; [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Indices.html" title="Index" rel="index">Index</a>]</p>
</div>
<hr>
<h4 class="subsection" id="MIPS-Paired_002dSingle-Support-1"><span>6.60.16 MIPS Paired-Single Support<a class="copiable-link" href="#MIPS-Paired_002dSingle-Support-1"> &para;</a></span></h4>

<p>The MIPS64 architecture includes a number of instructions that
operate on pairs of single-precision floating-point values.
Each pair is packed into a 64-bit floating-point register,
with one element being designated the &ldquo;upper half&rdquo; and
the other being designated the &ldquo;lower half&rdquo;.
</p>
<p>GCC supports paired-single operations using both the generic
vector extensions (see <a class="pxref" href="Vector-Extensions.html">Using Vector Instructions through Built-in Functions</a>) and a collection of
MIPS-specific built-in functions.  Both kinds of support are
enabled by the <samp class="option">-mpaired-single</samp> command-line option.
</p>
<p>The vector type associated with paired-single values is usually
called <code class="code">v2sf</code>.  It can be defined in C as follows:
</p>
<div class="example smallexample">
<pre class="example-preformatted">typedef float v2sf __attribute__ ((vector_size (8)));
</pre></div>

<p><code class="code">v2sf</code> values are initialized in the same way as aggregates.
For example:
</p>
<div class="example smallexample">
<pre class="example-preformatted">v2sf a = {1.5, 9.1};
v2sf b;
float e, f;
b = (v2sf) {e, f};
</pre></div>

<p><em class="emph">Note:</em> The CPU&rsquo;s endianness determines which value is stored in
the upper half of a register and which value is stored in the lower half.
On little-endian targets, the first value is the lower one and the second
value is the upper one.  The opposite order applies to big-endian targets.
For example, the code above sets the lower half of <code class="code">a</code> to
<code class="code">1.5</code> on little-endian targets and <code class="code">9.1</code> on big-endian targets.
</p>
</div>



</body>
</html>
